Molded parts such as those in molding beauty panels for golf carts, bumpers, and other molded exterior parts desire high gloss, good weatherability, and high impact strength. Examples of blends of ionomers with polyamides, see e.g., U.S. Pat. Nos. 3,845,163; 5,866,658; and 5,091,478.
Zinc stearate has been used to improve the flow and mold release properties of ionomers such as Surlyn Reflection® available from E. I. du Pont de Nemours and Company, Wilmington, Del., USA (DuPont). While compositions comprising certain polyamide such as Nylon 6 may have sufficient mold release performance, however, those based on other polyamide such as Nylon 12 do not. Increasing the level of zinc stearate to a point where mold release is acceptable can unfortunately produce a composition with poor weld-line strength and impact resistance.
Improved mold release allows shorter cycle times for improved process economics and can allow higher mold temperatures for improved surface gloss and scratch resistance from a harder surface of the molded part.
In commercial operations, mold release agent, generally a polymer or a combination of polymers, can be an emulsion or dispersion in a solvent. If dispersed in a solvent, the solvent is used as a vehicle to wet the surface of a shaped-determining mold, onto which the release agent is applied. There is an increasing need to develop a new composition comprising an ionomer/polyamide blend and having good mold release properties.